1. Field of the Invention
The present invention relates to retroviral protease inhibitors and, more particularly relates to novel compounds and a composition and method for inhibiting retroviral proteases. This invention, in particular, relates to N-heterocyclic moiety-containing hydroxyethylamine protease inhibitor compounds, a composition and method for inhibiting retroviral proteases such as human immunodeficiency virus (HIV) protease and for treatment or prophylaxis of a retroviral infection, e.g., an HIV infection. The subject invention also relates to processes for making such compounds as well as to intermediates useful in such processes.
2. Related Art
During the replication cycle of retroviruses, gag and gag-pol gene products are translated as proteins. These proteins are subsequently processed by a virally encoded protease (or proteinase) to yield viral enzymes and structural proteins of the virus core. Most commonly, the gag precursor proteins are processed into the core proteins and the pol precursor proteins are processed into the viral enzymes, e.g., reverse transcriptase and retroviral protease. It has been shown that correct processing of the precursor proteins by the retroviral protease is necessary for assembly of infectious virons. For example, it has been shown that frameshift mutations in the protease region of the pol gene of HIV prevents processing of the gag precursor protein. It has also been shown through site-directed mutagenesis of an aspartic acid residue in the HIV protease the processing of the gag precursor protein is prevented. Thus, attempts have been made to inhibit viral replication by inhibiting the action of retroviral proteases.
Retroviral protease inhibition typically involves a transition-state mimetic whereby the retroviral protease is exposed to a mimetic compound which binds (typically in a reversible manner) to the enzyme in competition with the gag and gag-pol proteins to thereby inhibit replication of structural proteins and, more importantly, the retroviral protease itself. In this manner, retroviral proteases can be effectively inhibited.
Several classes of mimetic compounds are known to be useful as inhibitors of the proteolytic enzyme renin. See, for example, U.S. Pat. No. 4,599,198; G.B. 2,184,730; G.B. 2,209,752; EP O 264 795; G.B. 2,200,115 and U.S. SIR H725. Of these, G.B. 2,200,115; G.B. 2,209,752; EP O 264,795; U.S. SIR H725; and U.S. Pat. No. 4,599,198 disclose urea-containing hydroxyethylamine renin inhibitors. However, it is known that, although renin and HIV proteases are both classified as aspartyl proteases, compounds which are effective renin inhibitors generally cannot be predicted to be effective HIV protease inhibitors.
Several classes of mimetic compounds have been proposed, particularly for inhibition of proteases, such as for inhibition of HIV protease. Such mimetics include hydroxyethylamine isoteres and reduced amide isosteres. See, for example, EP O 346 847; EP O 342,541; Roberts et al, "Rational Design of Peptide-Based Proteinase Inhibitors," Science, 248, 358 (1990); and Erickson et al, "Design Activity, and 2.8 .ANG. Crystal Structure of a C.sub.2 Symmetric Inhibitor Complexed to HIV-1 Protease," Science, 249, 527 (1990). EP O 346 847 discloses certain N-heterocyclic moiety-containing hydroxyethylamine protease inhibitor compounds, but does not suggest or disclose those of the present invention.
While it has been suggested that no improvement in the in vitro or ex vivo potency of hydroxyethyl-amine based inhibitors of HIV-protease containing a P.sub.2 asparagine can be made (Science, Roberts et al.), we find that this is not the case. Not only have we made in vitro and ex vivo improvements over P.sub.2 asparagine containing inhibitors, but the novel moieties reported herein are expected to permit certain allowances over the aforementioned reference including proteolytic stability, duration of action in vivo and pharmacokinetic profile.